Glacio-lacustrine sediments are deposited by glacial meltwater in lakes. These lakes include ice margin lakes or other types formed from glacial erosion or deposition. Sediments in the bedload and suspended load of meltwater streams are carried into lakes and deposited.
The bedload of a stream (mostly sands and gravels) is deposited at the lake margin (e.g., deltas), while the suspended load is deposited all over the lake. Sediments that are carried in the suspended load of a stream (commonly silts and clays) are transported into the lake in suspension or by currents along the lake floor.
Particles in the suspended load tend to be larger in summer, when glacier melt results in high amounts of turbid meltwater entering the lake. These larger particles settle quickly over the lake bottom. During the winter, freezing temperature reduces discharge of inbound streams and may result in a frozen lake surface. The lake water is very calm and this is when the finer particles settle. This annual cycle of deposition produces layered sediments known as rhythmites. Each annual layer of sediment is called a varve.